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The mission of the Center for Disease and Vector Research is to develop and implement technologies that will alleviate the medical and economic burden exacted by infectious diseases and vector-borne diseases in human and plants. The Center achieves this through cross-disciplinary research by combining expertise in molecular biology, nanotechnology, gene silencing and the genomics-based sciences with expertise in insect pest control. Our goal is to provide practical solutions within therapeutic and economic time frames.

In plants as in other complex eukaryotes, the circadian clock influences a wide range of biological processes. Since plants are rooted in their environment, they make an excellent model system for investigating how organisms can integrate internal temporal information generated by the clock with environmental cues to control physiological pathways. We are currently investigating the roles of these internal and external signals in the control of growth and development in sunflower. Sunflowers are famous for their ability to track the sun, alternatively called heliotropism or solar tracking. Solar tracking involves both the continual orientation of the apex towards the sun throughout the day and the gradual re-orientation of the apex from west to east at night in anticipation of sunrise. We have found that solar tracking behavior is regulated by the circadian clock, is mediated by differential growth on opposite sides of the stem, and that its disruption significantly impacts plant biomass and total leaf area. Transcriptional analysis has suggested auxin-mediated growth pathways control this tracking behavior, a possibility that we are now investigating. Interestingly, solar tracking in sunflower ceases upon flower maturation, with the flower heads facing east. We find that sunflower phototropic responses are gated by the clock, with maximal bending occurring when plants are exposed to directional light in the morning. Combined with the gradual cessation of stem growth upon flower maturation, this may explain why sunflowers face east at maturity. In ongoing work, we are examining the effects of this eastward orientation on floret maturation and its ecological consequences.